Noise Reduction in a Thermostatic Expansion Valve

ABSTRACT

A thermostatic expansion valve assembly is provided for an air conditioning system. A thermostatic expansion valve includes a valve body having an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid inlet port. The thermostatic expansion valve controls a flow of refrigerant from the liquid line port to the evaporator inlet port. A liquid line conduit is coupled to the liquid inlet port. The liquid line conduit has at least a segment elevated above the liquid inlet port. The vapor within the liquid inlet conduit accumulates at an uppermost portion of the segment prior to a compressor startup. A substantial amount refrigerant liquid is maintained between the uppermost portion of the segment and the liquid inlet port prior to the compressor startup.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates in general to air conditioning systems, and in particular to noise reduction in a thermostatic expansion valve.

2. Background of Related Art

A closed loop refrigeration system is utilized in a vehicle to provide conditioned air to a vehicle interior to cool and de-humidify the interior of a vehicle. A thermostatic, or thermal, expansion valve controls the flow of refrigerant through the closed loop refrigerant system. The thermostatic expansion valve senses the temperature and pressure of the refrigerant at the outlet of an evaporator and adjusts the opening and closing of a valve element within the thermostatic expansion valve to control the amount of refrigerant flowing through the evaporator, and thus the superheat at the outlet of the evaporator.

During a compressor off period in the closed loop refrigerant system, refrigerant in the liquid line conduit being supplied to the liquid line port (Port A) may absorb heat and vaporize. If the vaporized refrigerant in the liquid line conduit occupies the region of the liquid line conduit in close relation to the liquid line port (Port A), then upon compressor startup the vapor disposed in close relation to the liquid line port (Port A) flows into the thermostatic expansion valve before being liquefied and subcooled. The sudden in-rush of vapor into the thermostatic expansion valve at compressor startup is a major, if not dominant, contributor to unwanted hiss noise.

BRIEF SUMMARY OF THE INVENTION

The present invention has the advantage of delaying vapor formed in the liquid line conduit during compressor-off period, from entering the thermostatic expansion valve during compressor startup which will reduce the noise generated during compressor startup.

In one aspect of the present invention, a thermostatic expansion valve assembly is provided for an air-conditioning system. A thermostatic expansion valve includes a valve body having an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid inlet port. The thermostatic expansion valve controls a flow of refrigerant from the liquid line port to the evaporator inlet port. A liquid line conduit is coupled to the liquid inlet port. The liquid line conduit has at least a segment elevated above the liquid inlet port. The vapor within the liquid inlet conduit accumulates at an uppermost portion of the segment prior to a compressor startup. A substantial amount refrigerant liquid is maintained between the uppermost portion of the segment and the liquid inlet port prior to the compressor startup.

In yet another aspect of the present invention, a vehicle air-conditioning system includes a compressor configured for pumping refrigerant. A condenser configured to receive the refrigerant from the compressor and to remove heat from the refrigerant. An evaporator configured to receive the refrigerant. The evaporator being exposed to ambient air for removing the heat from the ambient air. A thermostatic expansion valve includes an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid inlet port. A liquid line conduit couples the liquid inlet port with the condenser, typically via a receiver. The liquid line conduit has at least a segment elevated above the liquid inlet port. The vapor within the liquid line conduit accumulates at the elevated segment during a compressor off-period.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an air-conditioning system for a vehicle of the present invention.

FIG. 2 illustrates a thermostatic expansion valve assembly according to a first preferred embodiment of the present invention.

FIG. 3 illustrates a thermostatic expansion valve assembly according to a second preferred embodiment of the present invention.

FIG. 4 illustrates a thermostatic expansion valve assembly according to a third preferred embodiment of the present invention.

FIG. 5 illustrates a thermostatic expansion valve assembly according to a fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated in FIG. 1 a vehicle air-conditioning system 10 for a vehicle 12. The vehicle air-conditioning system 10 is a closed loop refrigeration system that includes a compressor 14, a condenser 16, an evaporator 18, and a thermostatic expansion valve 20. Typically, the system 10 also includes a receiver or a receiver-drier 15.

Referring to FIGS. 1 and 2, the thermostatic expansion valve 20 includes a valve body 21 having a liquid inlet port (commonly known as Port A) 22, an evaporator inlet port (commonly known as Port B) 24, an evaporator outlet port (commonly known as Port C) 26, and a suction line port (commonly known as Port D) 28. The compressor 14 pumps refrigerant within the closed loop system. The refrigerant then flows through the condenser 16. The condenser 16 cools and condenses the refrigerant. The thermostatic expansion valve 20 senses the temperature and pressure of the refrigerant exiting the evaporator 18 and actuates a valve member within the thermostatic expansion valve 20 for controlling the amount of refrigerant flowing through the evaporator 18 and thus achieving a desired cooling performance, by targeting a predetermined or preset superheat at the evaporator outlet port 28. The refrigerant flows through the thermostatic expansion valve 20 and into the evaporator 18 where blown air is passed. The refrigerant absorbs heat from the air as it flow through the evaporator 18. The cooled air is used to cool the interior of a vehicle. The receiver-drier 15 separates vapor and liquid with the liquid being channeled to the thermal expansion valve 20 for its desired function. It also serves to remove moisture and filter out dirt and contaminants from the refrigerant.

FIG. 2 illustrates the thermostatic expansion valve and liquid line assembly. A liquid line conduit 30 is coupled to the liquid inlet port 22 of the thermostatic expansion valve 20. The liquid line conduit 30 includes at least one segment 32 that is elevated above the liquid inlet port 22. Vapor formed in the liquid line conduit 30 as a result of the refrigerant absorbing heat, being de-pressurized and vaporizing in the liquid line conduit 30 while the compressor 14 is in a non-operational state will flow and gather to an uppermost portion 34 of the segment 32 prior to compressor startup. The segment 32 of the liquid line conduit 30 increases in elevation as the segment 32 extends to the uppermost portion 34 for directing the vapor formed in the liquid line conduit 30 to flow to the uppermost portion 34. In prior art systems, the liquid line conduit runs up to, as opposed of down to, the liquid line inlet port 22 since the thermostatic expansion valve 20 is positioned at a higher elevation than the receiver-drier 15.

The liquid line conduit 30 is of a combined length and width or cross-section area such that a substantial portion of the liquid refrigerant is maintained between vapor collected at the uppermost portion 34 of the segment 32 and the liquid line inlet port 22 prior to compressor startup. As a result, vapor collected at the uppermost portion 34 is delayed from entering the thermostatic expansion valve 20 following the compressor startup. Preferably, the vapor is liquefied and sub-cooled through a pressurization process before being able to reach the thermostatic expansion valve 20. The delay in the vapor entering the thermostatic expansion valve 20 reduces noise peak that would otherwise be generated by having the vapor entering the thermostatic expansion valve 30 at a transient peak flow rate which typically is about three to five seconds after a compressor startup.

The volume of refrigerant maintained between the uppermost portion 34 and the liquid inlet port 22 is based on a length of the segment, and the inner diameter or width of the liquid line conduit 30. This results in a continuous stream of refrigerant liquid being supplied to the thermostatic expansion valve 20 for a predetermined period of time after compressor startup for reducing the noise generated. The predetermined internal volume of refrigerant maintained in the liquid line conduit for maintaining the continuous stream of refrigerant for the predetermined period of time after compressor startup is based on the size of the air-conditioning system (e.g., at least 1 ounce of refrigerant, at least 3 ounces of refrigerant, at least 5 ounces of refrigerant, etc).

FIGS. 3 and 4 illustrate a second and third preferred embodiment of the thermostatic expansion valve assembly, respectively. FIGS. 3 and 4 are similar to FIG. 2 and so, in order to avoid unnecessary repetition, FIGS. 3 and 4 will use the same element numbers for corresponding elements in FIG. 2. The liquid line conduit 30 includes insulation 38 for minimizing the heating of the refrigerant fluid within the liquid line conduit 30, which reduces vaporization during a compressor off-period and also increases the system efficiency during a compressor operation-period. Furthermore, a substantial portion of the liquid line conduits are made of aluminum, which has a high thermal conductivity. The liquid line conduit 30 or a portion of the liquid line conduit may be made of rubber or some other flexible material/structure (such as low permeation, nylon-reinforced hose) that typically has a low thermal conductivity, that is, a lower thermal conductivity than that of aluminum, further minimizing the heat absorption by the refrigerant fluid within the liquid line conduit 30. Moreover, the liquid line conduit 30 may be routed in a region of the vehicle spaced from a vehicle heat generating source (e.g., engine block) for limiting the thermal absorption of the liquid line conduit 30. If the routing of the liquid line conduit 30 is not capable of being routed in an area away from a heat generating source, then a thermal barrier 40 may be used to reduce the thermal absorption by the liquid line conduit 30 as shown generally in FIG. 4.

FIG. 5 illustrates a fourth preferred embodiment of the thermostatic valve. FIG. 5 is similar to FIG. 2 and so, in order to avoid unnecessary repetition, FIG. 5 will use the same element numbers for corresponding elements in FIG. 2. In FIG. 5, the segment 32 may include an optional trap 42 formed directly before the liquid inlet port 22 as shown in FIG. 4. The trap 42 increases available liquid volume and assists in maintaining liquid refrigerant in the liquid line conduit 30 proximal to the thermostatic expansion valve 20. Alternatively, the trap may include non-conduit form such as an accumulator or a bottle/canister.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope. 

1. A thermostatic expansion valve assembly for an air conditioning system, the assembly comprising: a thermostatic expansion valve including a valve body having an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid inlet port, the thermostatic expansion valve controlling a flow of refrigerant from the liquid line port to the evaporator inlet port; and a liquid line conduit coupled to the liquid inlet port, the liquid line conduit having at least a segment elevated above the liquid inlet port, wherein vapor within the liquid inlet conduit accumulates at an uppermost portion of the segment prior to a compressor startup, and wherein a substantial amount of refrigerant liquid is maintained between the uppermost portion of the segment and the liquid inlet port prior to the compressor startup.
 2. The thermostatic expansion valve assembly of claim 1 wherein the liquid line between the uppermost portion of the segment and the liquid inlet port forms a liquid trap.
 3. The thermostatic expansion valve assembly of claim 1 wherein the liquid line conduit between the uppermost portion and the liquid inlet port is of a predetermined length which contains refrigerant liquid and provides a continuous stream of refrigerant liquid for a predetermined period of time after the compressor startup for reducing the noise generated following the compressor startup.
 4. The thermostatic expansion valve assembly of claim 3 wherein the liquid line is of a predetermined diameter for maintaining the continuous flow of refrigerant liquid to the thermal expansion valve for the predetermined period of time following the compressor startup.
 5. The thermostatic expansion valve assembly of claim 4 wherein a segment of the liquid line conduit between the liquid inlet port and the uppermost portion includes at least a predetermined internal volume for maintaining the continuous flow of refrigerant liquid to the thermal expansion valve for the predetermined period of time following the compressor startup.
 6. The thermostatic expansion valve assembly of claim 5 wherein the predetermined internal volume is at least five ounces.
 7. The thermostatic expansion valve assembly of claim 5 wherein the predetermined internal volume is at least three ounces.
 8. The thermostatic expansion valve assembly of claim 5 wherein the predetermined internal volume is at least one ounce.
 9. The thermostatic expansion valve assembly of claim 1 wherein the liquid line conduit increases in elevation to the uppermost portion for directing vapor formed in the liquid line conduit between the liquid inlet port and the uppermost portion to flow toward the uppermost portion.
 10. The thermostatic expansion valve assembly of claim 1 wherein the liquid line conduit includes insulation for insulating at least a portion of the liquid line conduit for minimizing a heating of refrigerant liquid within the liquid line conduit during a compressor off-period.
 11. A vehicle air-conditioning system comprising: a compressor configured to pump refrigerant; a condenser configured to receive the refrigerant from the compressor and removing heat from the refrigerant; an evaporator configured to receive the refrigerant, the evaporator being exposed to ambient air for removing the heat from the ambient air; a thermostatic expansion valve including an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid inlet port; and a liquid line conduit coupled between the condenser and the liquid inlet port, the liquid line conduit having at least a segment elevated above the liquid inlet port, wherein vapor within the liquid line conduit accumulates at the elevated segment during a compressor off-period.
 12. The vehicle air-conditioning system of claim 11 wherein the liquid line includes a liquid trap.
 13. The vehicle air-conditioning system of claim 11 wherein a substantial amount of the refrigerant is maintained as a liquid between an uppermost portion of the elevated segment and the liquid inlet port prior to compressor startup.
 14. The vehicle air-conditioning system of claim 11 wherein the liquid line conduit is of a predetermined length from the liquid inlet port and the uppermost portion for maintaining a continuous flow of the liquid refrigerant to the thermal expansion valve for a predetermined period of time following the compressor startup.
 15. The vehicle air-conditioning system of claim 14 wherein the liquid line conduit is of a predetermined diameter for maintaining the continuous flow of the liquid refrigerant to the thermal expansion valve for the predetermined period of time following the compressor startup.
 16. The vehicle air-conditioning system of claim 11 wherein the portion of the liquid line conduit between the liquid line port and the uppermost portion includes at least a predetermined internal volume of the refrigerant for maintaining a continuous flow of the liquid refrigerant to the thermal expansion valve for the predetermined period of time following the compressor startup.
 17. The vehicle air-conditioning system of claim 11 wherein the liquid line conduit includes insulation for insulating at least a portion of the liquid line conduit for minimizing a heating of refrigerant fluid within the liquid line conduit.
 18. The vehicle air-conditioning system of claim 11 wherein the liquid line is made of a predetermined material having a thermal conductivity lower than that of aluminum for substantially limiting the thermal absorption by the liquid line conduit.
 19. The vehicle air-conditioning system of claim 11 wherein the liquid line conduit is configured to be routed in an area of the vehicle spaced from a vehicle heat generating source for limiting the thermal absorption by the liquid line conduit.
 20. The vehicle air-conditioning system of claim 11 wherein the liquid line conduit is configured to be routed behind a thermal barrier for limiting the thermal absorption by the liquid line conduit. 